The present invention relates to a CSI extraction method in a MIMO receiver used in a wireless communication system, the method including: obtaining an effective channel matrix by matrix multiplication of a precoding matrix and a channel estimation value obtained through a CSI-RS; calculating an upper and a lower bound of a minimum distance for each layer through QR decomposition for the effective channel matrix; and mapping the upper and the lower bound of the minimum distance for each layer to each codeword, and extracting a mean mutual information per bit (MMIB) metric that is a transmission capacity per unit frequency for each codeword. According to the present invention, QR decomposition and a MMIB metric are used to obtain the minimum distance for each layer without a multidimensional search process, whereby the CSI is extracted with fewer operations than the conventional method when the MIMO transmission order is high.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A channel state information (CSI) extraction method in a multiple-input and multiple-output (MIMO) receiver used in a wireless communication system, the method comprising: obtaining a channel state information reference signal (CSI-RS); obtaining an effective channel matrix for each of a plurality of candidate ranks and a plurality of corresponding candidate precoding matrices and the effective channel matrix is determined by matrix multiplication of a candidate precoding matrix corresponding to each of the plurality of candidate ranks and a channel estimation value obtained through the channel state information reference signal (CSI-RS), wherein each of the plurality of candidate ranks includes at least one layer; calculating an upper bound and a lower bound of a minimum distance for each layer for each of the plurality of candidate ranks and each of the plurality of corresponding candidate precoding matrices through QR decomposition for the effective channel matrix; mapping the upper bound and the lower bound of the minimum distance for each layer for each of the plurality of candidate ranks and each of the plurality of corresponding candidate precoding matrices to a corresponding one of a plurality of codewords; and extracting a mean mutual information per bit (MMIB) metric that is a transmission capacity per unit frequency for each of the plurality of codewords for each of the plurality of candidate ranks and each of the corresponding candidate precoding matrices.
2. The method of claim 1 , further comprising: determining a sum of MMIB by adding all the MMIB for each of the plurality of unit frequencies and for each of the plurality of codewords; determining a maximum sum of MMIB among the sum of MMIB for each of the plurality of candidate ranks and the plurality of corresponding candidate precoding matrices; determining the channel state information from a transmission capacity of an effective channel based on the maximum MMIB metric, wherein the channel state information includes a rank indicator (RI), a precoding matrix indicator (PMI) and a channel quality indicator (CQI) corresponding to the maximum MMIB.
3. The method of claim 1 , wherein the MMIB metric is calculated through a sum process where a predetermined weighting is given to the upper bound and the lower bound.
4. The method of claim 1 , further comprising: determining the rank indicator (RI) included in the channel state information as a rank value of the precoding matrix having the maximum sum of the MMIB metrics of all subcarriers of the channel state information reference signal which is present in all observation bands.
5. The method of claim 1 , further comprising: determining the precoding matrix indicator (PMI) included in the channel state information by selecting the precoding matrix having the maximum sum of the MMIB metrics in all observation bands, among the precoding matrixes having a predetermined rank indicator (RI).
6. The method of claim 1 , further comprising: determining the precoding matrix indicator (PMI) included in the channel state information by selecting the precoding matrix having the maximum sum of the MMIB metrics for each sub-band, among the precoding matrixes having a predetermined rank indicator (RI).
7. The method of claim 1 , further comprising: selecting the channel quality indicator (CQI) included in the channel state information by using a table look-up method in accordance with a characteristic of a channel, from a transmission quality per codeword (ppCINR) obtained through MMIB inverse transformation, after an average of values of the MMIB metrics in all bands is obtained by applying the precoding matrix having a predetermined precoding matrix indicator (PMI) value.
8. The method of claim 1 , wherein the upper bound and the lower bound are determined on the basis of diagonal elements of a triangular matrix generated through the QR decomposition for the effective channel matrix.
9. The method of claim 1 , wherein when multiple MIMO symbols are mapped to one codeword, a value of the MMIB metric of the codeword is the minimum value among values of the MMIB metrics for the respective MIMO symbols.
10. The method of claim 1 , wherein the QR decomposition is performed on each of matrixes resulting from column flipping of the effective channel matrix and the effective channel matrix.
11. A non-transitory, computer-readable recording medium having a program recorded thereon for executing a channel state information (C SI) extraction method in a multiple-input and multiple-output (MIMO) receiver used in a wireless communication system, the method comprising: obtaining a channel state information reference signal (CSI-RS); obtaining an effective channel matrix for each of a plurality of candidate ranks and a plurality of corresponding candidate precoding matrices and the effective channel matrix is determined by matrix multiplication of a candidate precoding matrix corresponding to each of the plurality of candidate ranks and a channel estimation value obtained through the channel state information reference signal (CSI-RS), wherein each of the plurality of candidate ranks includes at least one layer; calculating an upper bound and a lower bound of a minimum distance for each layer for each of the plurality of candidate ranks and each of the plurality of corresponding candidate precoding matrices through QR decomposition for the effective channel matrix; mapping the upper bound and the lower bound of the minimum distance for each layer for each of the plurality of candidate ranks and each of the plurality of corresponding candidate precoding matrices to a corresponding one of a plurality of codewords; and extracting a mean mutual information per bit (MMIB) metric that is a transmission capacity per unit frequency for each of the plurality of codewords for each of the plurality of candidate ranks and each of the corresponding candidate precoding matrices.
12. A MIMO receiver used in a wireless communication system, the MIMO receiver comprising: a channel state analysis unit configured to: obtain a channel state information reference signal (CSI-RS), obtain an effective channel matrix for each of a plurality of candidate ranks and a plurality of corresponding candidate precoding matrices and the effective channel matrix is determined by matrix multiplication of a candidate precoding matrix corresponding to each of the plurality of candidate ranks and a channel estimation value obtained through the channel state information reference signal (CSI-RS), wherein each of the plurality of candidate ranks includes at least one layer, calculate an upper bound and a lower bound of a minimum distance for each layer for each of the plurality of candidate ranks and each of the plurality of corresponding candidate precoding matrices through QR decomposition for the effective channel matrix, map the upper bound and the lower bound of the minimum distance for each layer for each of the plurality of candidate ranks and each of the plurality of corresponding candidate precoding matrices to a corresponding one of a plurality of codewords, and extract a mean mutual information per bit (MINIM) metric that is a transmission capacity per unit frequency for each of the plurality of codewords for each of the plurality of candidate ranks and each of the corresponding candidate precoding matrices; and a channel state information determination unit configured to: determine a sum of MMIB by adding all the MINIM for each of the plurality of unit frequencies and for each of the plurality of codewords, determine a maximum sum of MMIB among the sum of MINIM for each of the plurality of candidate ranks and the plurality of corresponding candidate precoding matrices; and determine the channel state information from a transmission capacity of an effective channel based on the maximum MMIB metric, wherein the channel state information includes a rank indicator (RI), a precoding matrix indicator (PMI) and a channel quality indicator (CQI) corresponding to the maximum MMIB.
13. The MIMO receiver of claim 12 , wherein in the determining of the sum of MMIB, a predetermined weighting is given to the upper bound and the lower bound.
14. The MIMO receiver of claim 12 , wherein the rank indicator (RI) included in the channel state information is determined as a rank value of the precoding matrix having the maximum sum of the MMIB metrics of all subcarriers of the channel state information reference signal which is present in all observation bands.
15. The MIMO receiver of claim 12 , wherein the precoding matrix indicator (PMI) included in the channel state information is determined selecting the precoding matrix having the maximum sum of the MMIB metrics in all observation bands, among the precoding matrixes having a predetermined rank indicator (RI).
16. The MIMO receiver of claim 12 , wherein the precoding matrix indicator (PMI) included in the channel state information is determined selecting the precoding matrix having the maximum sum of the MMIB metrics for each sub-band, among the precoding matrixes having a predetermined rank indicator (RI).
17. The MIMO receiver of claim 12 , wherein the channel quality indicator (CQI) included in the channel state information is selected using a table look-up method in accordance with a characteristic of a channel, from a transmission quality per codeword (ppCINR) obtained through MMIB inverse transformation, after an average of values of the MMIB metrics in all bands is obtained by applying the precoding matrix having a predetermined precoding matrix indicator (PMI) value.
18. The MIMO receiver of claim 12 , wherein the upper bound and the lower bound are determined on the basis of diagonal elements of a triangular matrix generated through the QR decomposition for the effective channel matrix.
19. The MIMO receiver of claim 12 , wherein when multiple MIMO symbols are mapped to one codeword, a value of the MMIB metric of the codeword is the minimum value among values of the MMIB metrics for the respective MIMO symbols.
20. The MIMO receiver of claim 12 , wherein the QR decomposition is performed on each of matrixes resulting from column flipping of the effective channel matrix and the effective channel matrix.
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January 22, 2020
February 23, 2021
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